How could I know whether the eCommerce site I use uses SET (Secure Electronic Transaction). I know SET is a standard. But I see only an SSL connection
As Avid pointed out, the SET standard was abandoned in favor of the 3-D Secure scheme; so no, it isn't really a standard. If I recall correctly, the protocol never really gained wide-acceptance due to its complexity and cost versus simply using SSL.
The chances that your ecommerce store use SET are very low (<1%). However, there is a simple way you can check to see if the ecommerce store uses SET... if you need to install an "e-wallet" client-side application, then you can rest assured you are using SET. However, not having to install the client-app won't tell you much because SET can be implemented on the backend server, in which case the problem of having to use an e-wallet is offloaded to the server in a way that is transparent to the user.
In the end, there isn't a 100% accurate way to tell whether or not you are using SET, but I think it's a moot point given its lack of acceptance or use.
According to Wikipedia (emphasis mine):
So, no, that site most probably is not using SET. And apparently, it shouldn't be.